cannot call member function without object

I get the following error when trying to connect two classes together:

Code:

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qapp.cpp: In static member function 'static bool QApp::eventFilter(void*)':
qapp.cpp:32: error: cannot call member function 'void QApp::mouseCoord(int, int, int, int, int)' without object

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main.cpp:

Code:

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int main(int argc, char *argv[])
{
    QApp a(argc, argv);
    Widget w;
    w.show();
 
    QObject::connect(&a,SIGNAL(mouseCoords(int, int, int, int, int)),
                     &w,SLOT(mouseCoords(int, int, int, int, int)));
 
    return a.exec();
}

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qapp.cpp:

Code:

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emit mouseCoord(get_raw_mouse_x_delta(i), get_raw_mouse_y_delta(i), // this is line 32...
                                      is_raw_mouse_button_pressed(i, 0), is_raw_mouse_button_pressed(i, 1), is_raw_mouse_button_pressed(i, 2));

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I have searched the forum and found several issues quite like mine, but not enough to help me out.

As the compiler error message says, you cannot call a member function, which requires a "this" pointer, from a static method that does not have a "this" pointer to give. This might do it:

Code:

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QApp *app = qobject_cast<QApp>(qApp);
app->mouseCoords(...);

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BTW: Is that mouseCoord() or mouseCoords() ? You aren't consistent.

If I do this:

Code:

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QApp *app = qobject_cast<QApp>(qApp);
      app->mouseCoords(...); // what is this exactly? Am I not supposed to use connect()?

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Then what happens to this?

Code:

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QApp a(argc, argv);

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Thanks for the help.

I would ask first why did you make your QApp::eventFilter() method static?

I made it static because that's the only way it would work with QAbstractEventDispatcher(). I was experiencing some difficulties with setting QAbstractEventDispatcher() filter and a thread here in QtCentre Forum said that I should make eventFilter() static, I did and it worked. Only for that reason. But if there is a better way I would really like to know.

EDIT:
if I remove "static" from eventFilter I get this error message:

Code:

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qapp.cpp: In constructor 'QApp::QApp(int&, char**)':
 
qapp.cpp:14: error: no matching function for call to 'QAbstractEventDispatcher::setEventFilter(<unresolved overloaded function type>)'
 
c:\Qt\2010.05\qt\include\QtCore/../../src/corelib/kernel/qabstracteventdispatcher.h:91: note: candidates are: bool (* QAbstractEventDispatcher::setEventFilter(bool (*)(void*)))(void*)

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But this method shouldn't be static. And if you make it static then you can't call non-static methods from it. What do you need QAbstractEventDispatcher for and what is that you can't make work without making eventFilter() static?

I need QAbstractEventDispatcher to be able to get WM_INPUT messages because winEvenFilter won't do it.

Quote:

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EDIT:
if I remove "static" from eventFilter I get this error message:

Code:

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qapp.cpp: In constructor 'QApp::QApp(int&, char**)':
 
qapp.cpp:14: error: no matching function for call to 'QAbstractEventDispatcher::setEventFilter(<unresolved overloaded function type>)'
 
c:\Qt\2010.05\qt\include\QtCore/../../src/corelib/kernel/qabstracteventdispatcher.h:91: note: candidates are: bool (* QAbstractEventDispatcher::setEventFilter(bool (*)(void*)))(void*)

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Can we see the exact code?

Yes. Here it is:
main.cpp:

Code:

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#include <QtGui/QApplication>
#include <QObject>
#include "widget.h"
#include "qapp.h"
 
 
int main(int argc, char *argv[])
{
    //QApp *app = qobject_cast<QApp>(qApp);
    QApp a(argc, argv);
    Widget w;
    w.show();
 
    QObject::connect(&a,SIGNAL(mouseCoord(int, int, int, int, int)),
                     &w,SLOT(mouseCoord(int, int, int, int, int)));
 
    return a.exec();
}

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qapp.cpp:

Code:

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extern "C"{
#include "raw_mouse.h"
}
#include "qapp.h"
#include <QDebug>
#include <QAbstractEventDispatcher>
#define WM_INPUT 0x00FF
 
QApp::QApp(int & argc, char ** argv) :
    QApplication(argc,argv)
{
    qDebug() << init_raw_mouse(1, 0, 1);
    qDebug() << raw_mouse_count();
    QAbstractEventDispatcher::instance(0)->setEventFilter(eventFilter);
 
 
 
}
 
 
bool QApp::eventFilter(void *msg)
{
    MSG *mess;
 
    mess = (MSG*)msg;
    //qDebug() << mess->message;
    switch(mess->message){
    case WM_INPUT:
        {
            add_to_raw_mouse_x_and_y((HANDLE)mess->lParam);
            for (int i = 0; i < raw_mouse_count(); i++){
                emit mouseCoord(get_raw_mouse_x_delta(i), get_raw_mouse_y_delta(i),
                                      is_raw_mouse_button_pressed(i, 0), is_raw_mouse_button_pressed(i, 1), is_raw_mouse_button_pressed(i, 2));
            }
 
        }
        return true;
    }
    return false;
}

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app.h:

Code:

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#ifndef QAPP_H
#define QAPP_H
 
#include <QApplication>
 
class QApp : public QApplication
{
    Q_OBJECT
public:
    explicit QApp(int & argc, char ** argv );
    //bool winEventFilter(MSG *message, long *result);
     static bool eventFilter(void *msg);
private:
 
signals:
    void mouseCoord(int x, int y, int btn1, int btn2, int btn3);
 
public slots:
 
};
 
#endif // QAPP_H

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Why not do it this way?

Code:

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bool myInputEventFilter(void*);
 
class QApp : public QApplication {
  Q_OBJECT
  friend bool myInputEventFilter(void *);
public:
  QApp(int argc, char **argv) : QApplication(argc, argv){
    init_raw_mouse(1, 0, 1);
    QAbstractEventDispatcher::instance(0)->setEventFilter(myInputEventFilter);
}
signals:
    void mouseCoord(int x, int y, int btn1, int btn2, int btn3);
};
 
// the following function may probably be made static so that it doesn't pollute the namespace
bool myInputEventFilter(void *msg) {
    MSG *mess = (MSG*)msg;
    QApp *app = (QApp*)qApp;
    switch(mess->message){
    case WM_INPUT:
        {
            add_to_raw_mouse_x_and_y((HANDLE)mess->lParam);
            for (int i = 0; i < raw_mouse_count(); i++){
                emit app->mouseCoord(get_raw_mouse_x_delta(i), get_raw_mouse_y_delta(i),
                                      is_raw_mouse_button_pressed(i, 0), is_raw_mouse_button_pressed(i, 1), is_raw_mouse_button_pressed(i, 2));
            }
 
        }
        return true;
    }
    return false;
}

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Great! Working perfectly now. Thanks Wysota.
What do you mean with "pollute the namespace"?

Quote:

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Originally Posted by been_1990

What do you mean with "pollute the namespace"?

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Try defining (in a different cpp file) a function called myInputEventFilter and taking a void* as input and you'll see for yourself.